Frit Fly

Stem boring fly

Stem boring fly larvae are known to attack turf grass, especially ryegrasses and fescues and bent grass species.  The adult is a tiny, black, shiny fly about 2mm long.  The larvae are white to translucent in color, about 4mm long, and pointed at the head end. The hind end is rounded to blunt and has two distinctive rounded projections that are visible upon close inspection with a magnifying glass.  The pupae are small, red/brown in colour, and can be seen around the site of the damaged plants.

Damage symptoms 

Individual grass stems are killed by the boring activity of the larvae. Usually, the seed head stems are destroyed.  But when high populations are present, entire turf grass areas can be destroyed. Luckily damage does not usually affect turf areas that are mown at heights that inhibit seedhead formation.


Normally three-generation cycles per year.  The first generation emerges in May and lays eggs on grass tillers on which the larvae feed.  The second generation emerge in July with the third emerging in August through September.  The larvae of the third generation feed slowly through the Autumn and winter and pupate the following Spring.

HANDY TIP: If the problem is severe then we would recommend an Insecticide treatment